Newbie:- Query with Private page

Hi all,
Very receontly i have joiined wordpress.. and still learning to know the space. So please bear with me if i am asking the obvious

I see that the static page option is a great idea.. but i also see the private page option. Here is where I am confused.

1. All pages appear as tabs ( acc to my template) — fine by me
2. Say.. I have page 1 and page 2 ( and user 1 and user 2)
3. I would want the user1 to access page 1 & user 2 to acces page 2 only
4. How can i go about achieving this..

Can anyone help me
PS:- I dont know what version of WP i am using..How do i find out about this?